Electrophotographic light-sensitive material containing a protease enzyme

ABSTRACT

An electrophotographic light-sensitive material wherein a photoconductive insulating layer comprises a finely powdered inorganic photoconductive compound and an insulating resinous binder, the surface of said insulating layer containing a protease enzyme in a state capable of being dissolved from said layer when a solvent for the enzyme is brought into contact with the surface of the layer.

United States Patent [72] Inventor Satorulionjo Asaka-shi, Japan [21] Appl. No. 811,628

[22] Filed Mar. 28, 1969 [45 Patented Oct. 26, 1971 [73] Assignee Fuji Photo Film Co., Ltd.

Kanagawa, Japan [32] Priority Mar. 28, 1968 [33] Japan [54] ELECTROPHOTOGRAPHIC LIGHT-SENSITIVE MATERIAL CONTAINING A PROTEASE ENZYME 6 Claims, N0 Drawings [52] US. Cl 96/l.5,

[51] 111:. ct G03g5/00, H01l13/00,C03c 1/00 50 Field ofSearch ..96/l.5, 102,

Primary Examiner-George F. Lesmes Assistant ExaminerM. B. Wittenberg Attorney-Sughure, Rothwell, Mion, Zinn and Macpeak ELECTROIPIHOTOGRAPHIC LIGHT-SENSITIVE MATERIAL CONTAINING A PROTIEASE ENZYME BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a novel electrophotographic lightsensitive material.

2. Description of the Prior Art There have been proposed recording processes utilizing enzymes (cf, U.S. Pat. application Ser. No. 699,780). Specifically, by using a fine powder of an enzyme the electrophotographic toner, an image containing the enzyme is formed which is pressed onto wet gelatin so that the gelatin undergoes gradual decomposition in conformity with the image, to thereby afford a gelatin relief.

There are other typical processes whereby an image is formed with a substance uniformly impeding the elution of enzyme or uniformly decreasing the enzymatic activity on a layer containing the enzyme. The image thus formed is subjected to the same procedure described above. To cite a typical and simple example, a toner image comprising a water-insoluble, thermoplastic-colored resinous material (such as an ordinary toner used for electrophotographic copying processes) is formed on an electrophotographic light sensitive layer containing an enzyme. The image is thermally fixed and is then pressed onto wet gelatin, giving rise to a gelatin relief.

SUMMARY OF THE INVENTION The present invention involves the utilization of an enzyme in the surface of an electrophotographic light-sensitive material insulating layer. The electrophotographic light-sensitive material generally comprises at least one photoconductive insulating layer which is composed of a finely powdered photoconductive inorganic compound and an insulating resinous binder. As stated, the surface of said insulating layer must contain protease enzyme in an amount of not less than 0.0001 percent by weight based on the components. Up to percent by weight may be utilized. The enzyme must be in a state capable of being dissolved out of the layer when a solvent for the enzyme is brought into contact with the surface of said layer.

Various preferred enzymes, inorganic photoconductive compounds and resinous binders are described in the specification.

It is, accordingly, one object of the present invention to provide an improved electrophotographic light-sensitive material.

It is a further object of the invention to provide an improved electrophotographic light-sensitive material especially useful for the formation of gelatin reliefs via enzyme elution process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention, as heretofore indicated, broadly relates to the electrophotographic light-sensitive material useful in processes wherein an image is formed with a substance uniformly impeding the elution of enzyme or uniformly decreasing the enzymatic activity on a layer containing the enzyme. Typically, this layer is the insulating layer of an electrophotographic light-sensitive material, and the image formed on this light-sensitive layer (containing the enzyme) is subjected to the elution process by means of a solvent for the enzyme. Of course, the enzyme must be in a state capable of being dissolved out by the enzyme solvent. Typically, a toner image comprising a water-insoluble, thermoplastic-colored resinous material (such as an ordinary electrophotographic copying process toner) is formed on an electrophotographic light-sensitive layer containing the enzyme. The image is then fixed, usually thermally, and is then pressed onto wet gelatin, giving rise to a gelatin relief due to the enzymatic action. The sensitive material used is characterized by the fact that it contains, at least in the surface portion thereof, protease protealytic enzyme in an amount greater than 0.0001 percent, but less than 5 percent, by weight, based on the total components making up the layer.

Since it is necessary that the enzyme dissolve out of the layer and react with the substrate in the subsequent relief forming operation, it must be contained in the dissolvable form or state in the layer. For this purpose, it is desirable that the layer have a porous structure. Therefore, a layer consisting of a mixture of a finely divided photoconductive substance with an insulating binder is most suitable.

The layer according to the present invention offers substantial advantages in the following points:

I. The enzyme itself is soluble in water and never illustrates a high electrically insulating property. However, the enzyme, though small in quantity, provides extremely high activity, so it is sufiicient to have the enzyme incorporated therein in a very small quantity. Without reference to the thickness of the sensitive layer, it is frequently sufiicient for the purposes of this invention to incorporate the enzyme in the range of several hundred to several tens of mg. per square meter of the layer.

Accordingly, the enzyme has very little or substantially no effect upon the electrophotographic characteristics.

II. As the electrophotographic sensitive layer essentially contains a hydrophobic binder as its principal ingredient, there is no possibility that the layer, in its usual state, will acquire a high water content. The enzyme is liable to destruction in the presence of water, but results have proven that the enzyme retains stability when it is contained in the hydrophobic electrophotographic layer. The application of the layer of the present invention is described below.

III. By using a water-insoluble toner (ordinary toners consisting of a thermoplastic material and a coloring material are water-insoluble) an image is obtained, and is fixed. It is then pressed onto wet gelatin, casein or albumin, and heated (if necessary) to produce a relief.

IV. Using as the toner a strongly acidic or basic substance, a pH zone under which the enzymatic activity is remarkably lowered can be imagewise formed, providing a master-image for gelatin relief.

V. Ifa heat ray-absorbing toner is used and the layer is exposed to infrared rays, then the enzyme present inside the layer beneath the toner image is selectively destroyed, because the enzyme is liable to destruction by heat.

The enzymes which are employed in this invention include those which originate in animals, such as pepsin, cathepsin, rennin, tryssin, chymotrypsin; plant protease such as bromelin, papin, chymopapain, ficin, asclepain; and bacteriotic protease such as basillus subtilis protease, etc.

Some of these enzymes, such as papain, and ficin, require activators such as cystine, glutathione, or ascorbic acid for exertion of enzymatic activity. Such activators may be added to the photoconductive coatings, if they have no detrimental effect on the electrophotographic property thereof, and, if they have, they may be contained in the layer to be reacted with the enzymes. The compositions usable in the sensitive layer include mixtures of such photoconductive substances as zinc oxide, zinc sulfide, cadmium sulfide, cadmium selenide, cadmium sulfoselenide, and titanium oxide of the rutile type, with various kinds of water-insoluble insulating resins. Inorganic photoconductors described in US. Pat. No. 3,121,007 and US. Pat. No. 3,121,006 are applicable in he layers for use in the present invention. Those insulating; resins which are liable to decomposition by the enzyme, such as gelatin and casein prepared as a rigid film, should be excluded.

Although the specific resinous binderphotoconductive inorganic compound material ratio is not critical, and prior art teachings in this respect may be utilized, it has been found to be most preferred to utilize an insulating resinous binder in an amount of from about 30 parts to about 10 parts by weight per parts by weight of photoconductive inorganic compound.

As insulating resinous binders used in this invention, alkyd resin, silicone resin, polyvinyl acetate, copolymers of vinyl chloride-vinyl acetate, polystyrene, cellulose ethers and cellulose esters are suitable. That is, insulating resinous binders described in US. Pat. No. 3,052,539 may be used in this invention. Organic photoconductive coatings having a porous structure which permits the dissolving out of an enzyme are also useful.

It is desirable that the film be prepared in a comparatively porous state so that water may easily permeate into the interior thereof. Where ZnO and alkyd resin or silicone resin are used, for example, such films can be obtained by incorporating 30 to parts by weight of such a resin into 100 parts by weight of ZnO. The zinc oxide may be spectrally sensitized by the technique described in US. Pat. No. 3,052,540 or British Pat. No. l,005,245.

Suitable supports or bases for the recording material of the present invention include metal plates, metallized plastic films, paper, and the like.

Generally, when the gelatin relief is produced by using the layer of this invention, it is difficult to obtain faithful reproduction of continuous tone, and consequently it is necessary to produce the toner by converting the relief into a halftone image. If careful control of enzymatic activity can be accomplished by means of the toner, then it is possible to reproduce a continuous tone image.

Gelatin reliefs thus prepared can be used for dye transfer techniques such as are described in, for example, Photographic Chemistry" by Pierre Glafkides, published by Fountain Press, London (pages 689 to 701 When the amount of enzyme to be added is less than 0.0001 percent by weight based on the components of the layer, the decomposition of polypeptides occurs too slowly to be practical. In contrast, when it is more than 5 percent, it is disadvantageous because the effect does not increase proportionally with the increase in the amount beyond the level mentioned.

The enzyme may exist uniformly throughout the entire layer or only in the surface layer of the insulating layer. What matters is that the concentration of the enzyme in the surface area must lie in the range set forth previously, and that it can be dissolved out of the layer in the presence of the solvent thereof.

EXAMPLE 1 To 100 parts (by weight) of finely pulverized photoconductive zinc oxide, 35 parts of styrene-modified alkyd resin varnish (involatile component 50 percent), and 0.1 part of cobalt naphthenate, there was added toluene to obtain a homogeneous dispersion. As the base, there was used a paper treated with LiCl to increase the electrical conductivity thereof. The dispersion was spread onto the base to a dry film thickness of 8p, and dried. The layer thus obtained exhibited an excellent electrophotographic property and was observed to possess a particularly slow dark attenuation property.

Separately, a sensitive layer was prepared by following the same procedure as above, except the 0.1 part of Puronase P, a proteolytic enzyme from Streptomyces giseus of ray fungi, manufactured by Kaken Kagaku, was incorporated in a finely pulverized state into the aforementioned composition. When the layer was tested for properties after drying, it was found to possess the same properties as the layer which contained no Puronase P. When a wet film of gelatin was pressed against the layer and maintained thereon at 40 C., the gelatin was observed to be decomposed in several minutes, suggesting that the enzyme was contained in the dissolved state in the layer.

EXAMPLE 2 The material of a sensitive layer containing no enzyme and prepared as in example 1 was spread to a film thickness of 4p. This layer was thermally cured, and there was coated thereon a coating mixture prepared by blending [00 parts of photoconductive zinc oxide, 44.5 parts of vinyl chloride-vinyl acetate resin varnish (involatile component 45 percent), five parts of ethylphthalyl ethyl glycolate as the plasticizer, 0.1 part of Puronase P, and a suitable amount of butyl acetate. Subsequently, there was added thereto small quantities of rose bengal, fluorescein, and bromophenol blue to a film thickness of about 2;. The layer thus obtained had a panchromatic response and therefore could produce a color-separation toner image through the use of a color separation filter.

On each of three separate sheets, there was given a blank electrostatic charge of negative polarity, there was projected thereon a color-separated light image using a contact screen and a color-separation filter (one of red, green, and blue) superimposed on a transparent color negative original, respectively. The sheet having an electrostatic latent image thus formed was thereafter treated with a liquid developer containing carbon black particles having their surfaces covered with very fine particles of vinyl chloride-vinyl acetate copolymer. As the toner possessed a negative electrical charge, there occurred a repulsion development to produce a color-separation positive image. Exposure to infrared rays served to fix the toner.

The reliefs thus prepared were satisfactorily used for conventional dye transfer processes.

In view of the above, it will be appreciated that the resinous binder-inorganic photoconductive compound combination of the present invention is noncritical therein, with the exceptions that the parameters heretofore indicated must be followed. Accordingly, so long as the resinous binders recited in the specification meet the parameters heretofore indicated, any type of resinous binder may be utilized, the same test being applied to the inorganic photoconductive compound.

It will be appreciated that by the utilization of the term porous, it is meant that the layer merely need illustrate that extent of porosity exhibited by the mixture of a finely divided photoconductive substance with an insulating binder. The only essential feature here is that the enzyme must be able to be dissolved out of the layer and to subsequently react with the substrate in the relief forming operation.

To further define the present invention, in its most preferred form, the minimum depth" which the surface must have is 0.5 microns.

In addition, the most common solvent utilized for the enzyme is water.

Further, the language heretofore utilized to describe the amount of enzyme present, i.e., several hundred to several tens of mg. per square meter of the layer, is to mean from about 800 to about 20 milligrams, respectively.

Finally, in example 2, the amount of butyl acetate utilized was parts, the amount of rose bengal was 10/1000 parts, the amount of fluorescein utilized was 20/1000 parts and the amount of bromophenol blue utilized was 10/1000 parts.

I claim:

1. An electrophotographic light-sensitive material comprising at least one photoconductive insulating layer comprising a finely powdered photoconductive inorganic compound and an insulating resinous binder, the surface layer of said insulating layer containing protease enzyme in an amount of not less than 0.0001 percent and up to 5 percent by weight based on the components making up the surface layer, said enzyme is contained therein being in a state capable of being dissolved out of the layer when a solvent for the enzyme is brought into contact with the surface of the said surface.

2. The electrophotographic light-sensitive material claimed in claim 1 wherein said photoconductive inorganic compound is a member selected from the group consisting of zinc oxide, zinc sulfide, cadmium sulfide, cadmium selenide, cadmium sulfoselenide and titanium oxide of rutile type.

3. The electrophotographic light-sensitive material claimed in claim 1 wherein said insulating resinous binder is a member selected from the group consisting of alkyd resin, silicone resin, polyvinyl acetate, copolymers of vinyl chloride-vinyl acetate, polystyrene, cellulose esters and cellulose ethers.

4. The electrophotographic light-sensitive material claimed in claim 1 wherein said protease is a member selected from the group consisting of pepsin, cathepsin, rennin, tryssin, chymotrypsin, bromelin, papin, chymopapain, ficin, asclepain, basillus subtilis protease.

5. The electrophotographic light-sensitive material claimed in claim 1 wherein the amount of said insulating resinous binder is from 30 parts to parts by weight to 100 parts by weight of said photoconductive inorganic compound.

6. The electrophotographic light-sensitive material claimed 

2. The electrophotographic light-sensitive material claimed in claim 1 wherein said photoconductive inorganic compound is a member selected from the group consisting of zinc oxide, zinc sulfide, cadmium sulfide, cadmium selenide, cadmium sulfoselenide and titanium oxide of rutile type.
 3. The electrophotographic light-sensitive material claimed in claim 1 wherein said insulating resinous binder is a member selected from the group consisting of alkyd resin, silicone resin, polyvinyl acetate, copolymers of vinyl chloride-vinyl acetate, polystyrene, cellulose esters and cellulose ethers.
 4. The electrophotographic light-sensitive material claimed in claim 1 wherein said protease is a member selected from the group consisting of pepsin, cathepsin, rennin, tryssin, chymotrypsin, bromelin, papin, chymopapain, ficin, asclepain, basillus subtilis protease.
 5. The electrophotographic light-sensitive material claimed in claim 1 wherein the amount of said insulating resinous binder is from 30 parts to 10 parts by weight to 100 parts by weight of said photoconductive inorganic compound.
 6. The electrophotographic light-sensitive material claimed in claim 5 wherein said photoconductive inorganic compound is zinc oxide and said insulating resinous binder is a member selected from the group consisting of alkyd resin and silicone resin. 